Attention has been paid to active filters for power conditioning which provide the following multifunctions: reactive power compensation; harmonic compensation; flicker/imbalance compensation; and voltage regulation. Active filters in a range of 50 kVA-60 MVA have been practically installed in Japan. In the near future, the term "active filters" will have a much wider meaning than it did in the 1970s. For instance, active filters intended for harmonic solutions are expanding their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumers, and harmonic damping throughout power distribution systems. This paper presents the present status of active filters based on state-of-the-art power electronics technology, and their future prospects and directions toward the 21st Century, including the personal views and expectations of the author.

/pdf/new-trends-in-active-filters-for-power-conditioning-53fp9l1t5v.pdf

New trends in active filters for power conditioning

This paper proposes a simple but effective method of electric brake with energy regeneration for a brushless DC motor of an electric vehicle (EV). During the braking period, the proposed method only changes the switching sequence of the inverter to control the inverse torque so that the braking energy will return to the battery. Compared with the presented methods, the proposed solution simultaneously achieves dual goals of the electric brake and the energy regeneration without using additional converter, ultracapacitor, or complex winding-changeover technique. Since the braking kinetic energy is converted into the electrical energy and then returns to the battery, the energy regeneration could increase the driving range of an EV. In addition to the braking period, the duration of release throttle is also included in the energy-regenerative mechanism such that the EV is similar to engine vehicles having the engine brake. Therefore, the electric brake can improve rider's comfort and enhance the EV's safety. Finally, the feasibility of the proposed method is demonstrated by experimental results. It shows that the driving range of the EV could be increased to about 16.2%.

A Cost-Effective Method of Electric Brake With Energy Regeneration for Electric Vehicles

The sodium-nickel chloride battery, commonly known as ZEBRA, has been used for an experimental electric vehicle (EV). These batteries are cheaper than Li-ion cells and have a comparable specific energy (in watt-hours per kilogram), but one important limitation is their poor specific power (in watts per kilogram). The main objective of this paper is to demonstrate experimentally that the combination of ZEBRA batteries and ultracapacitors (UCAPs) can solve the lack of specific power, allowing an excellent performance in both acceleration and regenerative braking in an EV. The UCAP system was connected to the ZEBRA battery and to the traction inverter through a buck-boost-type dc-dc converter, which manages the energy flow with the help of DSP controllers. The vehicle uses a brushless dc motor with a nominal power of 32 kW and a peak power of 53 kW. The control system measures and stores the following parameters: battery voltage, car speed to adjust the energy stored in the UCAPs, instantaneous currents in both terminals (battery and UCAPs), and present voltage of the UCAP. The increase in range with UCAPs results in more than 16% in city tests, where the application of this type of vehicle is being oriented. The results also show that this alternative is cheaper than Li-ion powered electric cars.

Electric Vehicle Using a Combination of Ultracapacitors and ZEBRA Battery

Since their basic compensation principles were proposed around 1970, active filters have been studied by many researchers and engineers aiming to put them into practical applications. Shunt active filters for harmonic compensation with or without reactive power compensation, flicker compensation or voltage regulation have been put on a commercial base in Japan, and their rating or capacity has ranged from 50 kVA to 60 MVA at present. In near future, the term of active filters will cover a much wider sense than that of active filters in the 1970s did. The function of active filters will be expanded from voltage flicker compensation or voltage regulation into power quality improvement for power distribution systems as the capacity of active filters becomes larger. This paper describes present states of the active filters based on state-of-the-art power electronics technology, and their future prospects toward the 21st century, including the personal view and expectation of the author.

/pdf/new-trends-in-active-filters-for-improving-power-quality-3yt2lhc05y.pdf

New trends in active filters for improving power quality

A solar cell or photovoltaic cell is a device which generates electricity directly from visible light. However, their efficiency is fairly low. So, the solar cell costs expensive according to other energy resources products. Several factors affect solar cell efficiency. This paper presents the most important factors that affecting efficiency of solar cells. These effects are cell temperature, MPPT (maximum power point tracking) and energy conversion efficiency. The changing of these factors improves solar cell efficiency for more reliable applications.

/pdf/critical-factors-that-affecting-efficiency-of-solar-cells-1tgcs3upcb.pdf

Critical Factors that Affecting Efficiency of Solar Cells

This paper describes a novel regenerative braking control scheme of electric power-assisted wheelchairs for safety driving on downhill roads. The ldquoelectric power-assisted wheelchairrdquo which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people; however, it has no braking system to suppress the wheelchair's velocity and brings the dangerous and fearful driving particularly on downhill roads. Therefore, this paper proposes a novel safety and efficient driving control scheme based on the regenerative braking system. This paper applies the regenerative braking system with the step-up chopper circuit serially connecting two motors and realizes the velocity feedback control with the variable duty ratio so that it tracks the optimal velocity based on the minimum Jerk model. In addition, the dynamic braking system is also applied at the low-speed range instead of the regenerative braking in order to suppress the acceleration. Some driving experiments on the practical downhill roads show the effectiveness of the proposed control system.

Novel Regenerative Braking Control of Electric Power-Assisted Wheelchair for Safety Downhill Road Driving

This paper describes a novel trajectory control scheme for power assisted wheelchair. Human input torque patterns are always intermittent in power assisted wheelchairs, therefore, the suitable trajectories must be generated also after the human decreases his/her input torque. This paper tries to solve this significant problem based on minimum jerk model minimizing the changing rate of acceleration. The proposed control system based on minimum jerk trajectory is expected to improve the ride quality, stability and safety. Some experiments show the effectiveness of the proposed method.

http://www.jstage.jst.go.jp/article/ieejeiss/125/7/125_7_1133/_pdf

Novel Driving Control of Power Assisted Wheelchair Based on Minimum Jerk Trajectory

This paper describes a novel step climbing control scheme for electric power assisted wheelchairs. "Electric power assisted wheelchair" which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people. This research aims at realizing the safe and reliable step climbing motion control of power assisted wheelchairs because power assisted wheelchairs are in danger of overturning backward when raising the front wheels due to the excessive driving torque and of stopping in front of steps when the rear wheels try to climb over steps due to the insufficient driving torque. This paper proposes a novel step climbing control scheme for power assisted wheelchairs based on driving mode switching. The first driving mode, "front wheel raising mode", applies torque control system with the variable assistance ratio to prevent the dangerous overturning. The second driving mode, "rear wheel climbing mode", applies position control system based on the polynomial trajctory to surely climb over steps and stop at the suitable position. The mode switching control based on these two driving modes can generate the safe and reliable step climbing motions. Some experiments show the effectiveness of the proposed control system.

Novel Step Climbing Control for Power Assisted Wheelchair Based on Driving Mode Switching

In this paper, we propose a flexible shoe system for biped robots to optimize energy consumption of the lateral plane motion. This shoe system is made to deform decline outside in the lateral plane and it can absorb the kinetic energy of the robot in the lateral plane. Furthermore, this hardware (shoes) and software (controller) can be easily applicable to the ordinary walking robot system. The effectiveness and characteristics of this system are confirmed by computer simulations and experimental results. It is confirmed that the stiffness of the shoe is a very important parameter for energy consumption by using computer simulations and experimental results.

A Study of Energy-Saving Shoes for Robot Considering Lateral Plane Motion

This paper describes a novel straight and circular road driving control scheme for electric power assisted wheelchairs. "Electric power assisted wheelchair" which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people, however, the performance of the straight and circular road driving must be further improved because the two wheels drive independently. This paper proposes a novel driving control scheme based on fuzzy algorithm to realize the stable and reliable driving on straight and circular roads. The suitable assisted torque of the right and left wheels is determined by fuzzy algorithm based on the posture angular velocity of the wheelchair and the human input torque proportion of the right and left wheels. Some experiments on the practical roads show the effectiveness of the proposed control system.

Susumu Tadakuma

Papers

Novel Regenerative Braking Control of Electric Power-Assisted Wheelchair for Safety Downhill Road Driving

Novel Driving Control of Power Assisted Wheelchair Based on Minimum Jerk Trajectory

Novel Step Climbing Control for Power Assisted Wheelchair Based on Driving Mode Switching

A Study of Energy-Saving Shoes for Robot Considering Lateral Plane Motion

Straight and Circular Road Driving Control for Power Assisted Wheelchair Based on Fuzzy Algorithm